1. Field of the Invention
This invention relates to a battery having an anode, a cathode and an electrolyte and which is appreciably improved in energy density.
This application claims the priority of the Japanese Patent Application No. 2002-265951 filed on Sep. 11, 2002, the entirety of which is incorporated by reference herein.
2. Description of Related Art
Recently, development in a lightweight secondary battery with a high energy density, as a power supply for electronic equipment such as a notebook personal computer, a portable telephone set and a VTR (video tape recorder) with a built-in camera, is progressing. Among the secondary batteries having the high energy density, there is a lithium secondary battery having an energy density larger than that of the aqueous electrolyte battery, exemplified by a lead battery, a nickel-cadmium battery or a nickel-hydrogen battery.
With the lithium secondary batteries, such inconveniences may arise that lithium tends to be precipitated on the anode during charging, while lithium precipitated by repetition of charging/discharging tends to grow in size in the form of dendrites, with the precipitated lithium being inactivated to lower the battery capacity.
Such a lithium ion secondary battery in which a carbonaceous material is used as an anode, is known as a secondary battery designed to overcome the problem. Specifically, the lithium ion secondary battery uses an anode obtained on compacting the carbonaceous material in a finely divided state along with a binder.
This lithium ion secondary battery exploits, as a battery reaction, such a reaction consisting in intercalating lithium between layers of a carbonaceous material used for an anode, such as graphite. For this reason, with the lithium ion secondary battery, a carbonaceous material, capable of doping/undoping lithium, is used as the anode active material. This prohibits lithium from becoming precipitated to the anode of the lithium ion secondary battery at the time of charging to achieve superior battery characteristics. With this lithium ion secondary battery, the carbonaceous material used for the anode is also stable in air, thus improving the yield in manufacturing the batteries.
With the above lithium ion secondary battery, in which the energy density can be larger than in the aqueous liquid electrolyte battery, it is requested to increase the energy density further in keeping up with the increasing power consumption in the electronic equipment of these days. In particular, with the lithium ion secondary battery, used in portable electronic equipment, it is requested to reduce the weight of the battery further and to increase its energy density, such that the weight reduction is a task of utmost importance.